SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cfaa6856bb9eec4c104092fdd08e2a695f312f0a567b28ea628c942ecb477500' 
  AND token = '3mhHste+ezGiMrOJ9KezOiwY/RvlrGZMhbTBI2bHkQ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}